CPAN has been online since October 1995 and is constantly growing. CPAN's main purpose is to provide a distributed repository for Perl programmers to locate, install, and share open source modules and code snippets.

Installable files on the CPAN are known as distributions. A distribution consists of one or more modules, documentation files, or scripts. Distributions are typically packaged with an install script called Makefile.PL or Build.PL.